A brief review of walking mechanics and knee anatomy will aid in an appreciation of the invention. The typical human walking cycle can be considered to begin with a heel strike to the ground, followed by a mid-stance phase in which the front of the foot lowers to the ground, pivoting about the grounded heel. The gait then transitions to a toe-off phase, in which the heel is lifted with an associated forward motion of the leg and body on the ball and toes of the foot. Ultimately, the foot is completely lifted from the ground and swung forward in a swing-through phase to the next heel strike. The other foot undertakes the same cycle of motion in a generally coordinated manner to provide forward locomotion.
During this complex motion, each knee transitions from a relatively straight extension at the heel strike to a rearward bend, or flexion, through the toe-off phase and returns to extension during the final swing-through phase. During the cycle, the weight of the patient is borne through the knee to varying degrees.
The human knee system can suffer a number of diseases that can affect the patient's ability to bear this weight and walk without pain. Perhaps the most often diagnosed disease is arthritis, which can affect the knee's medial compartment, located toward the body center, or the lateral compartment, located opposite the medial compartment on the outer side of the knee. In some circumstances, the patellofemoral compartment is also affected. The malfunction frequently occurs in one compartment, but some cases involve arthritis in two or three compartments of the knee.
A number of braces have been developed in the past to address uni-compartmental osteoarthritis by shifting the distribution of the pressure on the knee during walking to the non-diseased compartment of the knee. For example, U.S. Pat. No. 5,302,169 to Taylor discloses a knee brace that adjustably braces the leg in a lateral or medial inclination to transfer pressure from the affected compartment to the relatively healthier compartment. Depending on the compartment to be aided, the brace can induce varus (bow-leggedness) or vulgas (knock-kneedness). The Taylor device and other known devices focus on controlling the distribution of forces within the knee system, using the calf and thigh directly adjacent the joint to leverage the desired force transfers among the knee compartments.
While these devices have enjoyed some success in treating uni-compartmental conditions, they are incapable of addressing bi- or tri-compartmental maladies. Because of the compartmental transfer approach to the design of these prior devices, a healthy compartment of the knee is required to receive and bear the transferred pressure.
A brace providing substantial knee isolation of the knee from weight while permitting walking is desirable. Such brace can provide a number of advantages. It can be universally applied to all varieties of uni-compartmental conditions as well as bi- and tri-compartmental conditions. Knee isolation during walking can also encourage exercise.
Exercise, particularly low impact activity such as water exercise, has been found to provide numerous health benefits, especially when contrasted to sedentary lifestyle. Yet, many arthritic patients are caught in the physical dilemma that their condition prevents them from being sufficiently mobile to obtain the necessary exercise at remote facilities, such as aquatic exercise centers. Traditional walking aids, such as crutches canes and walkers, can often discourage patients from moving to exercise, perpetuating the problem and culminating in the need for corrective surgery.